Configurable photo detector circuit

ABSTRACT

A configurable photo detector circuit comprises a photo detector array including a plurality of photo detectors coupled to a plurality of amplifiers. A method for programming a detection pattern of the configurable photo detector circuit comprises selecting a first detection pattern for the photo detector array, generating first signals to create the first selected detection pattern, and applying the first generated signals to the photo detector circuit to implement the first selected detection pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/328,401 entitled “CONFIGURABLE PHOTO DETECTOR CIRCUIT” (currentlypending) filed Dec. 16, 2011 (the '401 application), which is adivisional of U.S. patent application Ser. No. 12/627,310 entitled“CONFIGURABLE PHOTO DETECTOR CIRCUIT” filed Nov. 30, 2009 (the '310application) which was issued as U.S. Pat. No. 8,097,840, which is adivisional of U.S. patent application Ser. No. 11/863,858 entitled“CONFIGURABLE PHOTO DETECTOR CIRCUIT” filed on Sep. 28, 2007 (the '858application) which issued as U.S. Pat. No. 7,635,836, which claimspriority to Provisional Application No. 60/890,942 entitled “FIELDPROGRAMMABLE PHOTO DETECTOR ARRAY” filed on Feb. 21, 2007 (the '942application). The '401 application, the '310 application, the '858application and the '942 application are each incorporated by referencein their entirety into the present application.

BACKGROUND

A conventional optical pick-up (OPU) apparatus enables information to berecorded, reproduced and erased with respect to a CD group disc (e.g.CD, CD-ROM, CD-R and CD-RW) and a DVD group disc (e.g. DVD, DVD-ROM,DVD-RAM, DVD-R and DVD-RW, DVD+R, DVD+RW), as well as to write/read morerecently introduced Blu-ray discs and/or HD-DVD format discs, withsingle or multiple layer formats. As known in the art, the OPU generallyhas an infrared semiconductor laser device for CD (about 780 nm), and ared semiconductor laser device for DVD (about 650 nm) and/or a bluelaser device for Blu-ray/HD-DVD (about 405 nm). The OPU includes photodetector IC (PDIC), and power monitor integrated circuit (PMIC), whichboth generally provide a fixed detection pattern.

In typical applications, each laser beam, such as infrared (780 nm forCD), red for DVD (about 650 nm) and blue (405 nm for Blu-ray and HD-DVD)is split to 3 beams by optical gratings, forming a central beam (zeroorder) and two side beams (first order). The center beam reads the discdata, while the side beams help to keep the beam in the disc track.

One problem during development of PDICs and PMICs for optical pickupunits (OPUs) relates to the need to select a photo detector detectionpattern before testing the system, since available photo detectorsprovide a fixed detection pattern and modeling is not currentlypossible. Unfortunately, testing may reveal a fixed pattern initiallyspecified does not provide the desired detector performance.

For example, one issue for the optical storage industry is related tothe unpredictable introduction of interference patterns on the servotracking signal caused by unwanted optical reflections when reading duallayer Blu-ray media. This issue can require a redesign of the photodetector patterns on the PDIC, thus leading to a time an expensive, timeconsuming and highly iterative design process.

SUMMARY

This Summary is provided to comply with 37 C.F.R. §1.73, requiring asummary of the invention briefly indicating the nature and substance ofthe invention. It is submitted with the understanding that it will notbe used to interpret or limit the scope or meaning of the claims.

A configurable photo detector circuit comprises a photo detector arrayincluding a plurality of photo detectors coupled to a plurality ofamplifiers. A method for programming a detection pattern of theconfigurable photo detector circuit comprises selecting a firstdetection pattern for the photo detector array, generating first signalsto create the first selected detection pattern, and applying the firstgenerated signals to the photo detector circuit to implement the firstselected detection pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

A fuller understanding of the present invention and the features andbenefits thereof will be accomplished upon review of the followingdetailed description together with the accompanying drawings, in which:

FIG. 1 shows a top level block diagram of a configurable photo detectorintegrated circuit according to an embodiment of the invention.

FIG. 2( a) shows an exemplary photo detector array according to anembodiment of the invention.

FIG. 2( b) shows an exemplary photodetector pattern layout for aconfigurable photo detector integrated circuit according to anembodiment of the invention.

FIG. 3 shows a switching matrix and output block for a configurablephoto detector circuit according to an embodiment of the invention.

FIG. 4 shows a configurable photo detector integrated circuit accordingto another embodiment of the present invention.

FIG. 5 shows a simplified exemplary circuit amplifier arrangementaccording to an embodiment of the invention.

FIG. 6 is a schematic of an exemplary optical pickup unit (OPU) that isprototyped using a configurable photo detector integrated circuitsaccording to an embodiment of the present invention.

FIG. 7 is a flow chart showing an exemplary method of prototyping an OPUusing a configurable photo detector circuit according to an embodimentof the invention.

DETAILED DESCRIPTION

Embodiments of the present invention are more particularly described inthe following description and examples that are intended to beillustrative only since numerous modifications and variations thereinwill be apparent to those of ordinary skill in the art. As used in thespecification and in the claims, the singular form “a,” “an,” and “the”may include plural referents unless the context clearly dictatesotherwise. Also, as used in the specification and in the claims, theterm “comprising” may include the embodiments “consisting of” and“consisting essentially of”.

A photo detector array integrated circuit having a field configurabledetection pattern according to an embodiment of the invention, generallyreferred to herein as a configurable photo detector circuit, comprises aphoto detector array comprising a plurality of photo detectors. Thephoto detectors may be grouped into banks. Each of the banks comprises aplurality of photo detectors for receiving light and outputtingelectrical signals. A switching matrix having a first plurality ofinputs is coupled to outputs of the plurality of photo detectors. Theswitching matrix is generally referred to herein as a two-dimensionalmatrix, based on the switching matrix having a plurality of rows andcolumns. The switching matrix also includes a second plurality of inputsfor receiving control signals which controls operation of the switches,such as for selecting from a plurality of different switchconfigurations. The switching matrix also provides a plurality of matrixoutputs. A controller is coupled to the second plurality of inputs ofthe switching matrix for controlling the switching matrix. In someembodiments, the controller includes a serial interface. The controllerallows users to use external programming to set specific ones of theplurality of different switch configurations. An output block comprisinga plurality of amplifiers is coupled to the switching matrix outputs forproviding a plurality of amplified outputs, wherein the electricalsignals from the photo detectors are generally directable to any of theplurality of amplifiers based on the externally programmable switchconfiguration.

As used herein, the term “photo detector array” refers to a plurality ofphoto detectors arranged in a pattern. The pattern can be a regularorder or arrangement, or an irregular and even random pattern of photodetectors.

Embodiments of the invention thus provide a method for programming adetection pattern of the configurable photo detector (such as PDICs andPMICs and related OPUs) which allow the user/customers to change andthus customize the photo detector detection pattern through iterativetesting of the photo detector array pattern. The photo detector patterncan be electronically changed until one or more performance relatedcriteria are obtained, thus removing much of the conventionaluncertainty associated with the user/customer investing in a custom ICwith a fixed photo detector pattern.

FIG. 1 shows a top level block diagram of a configurable photo detectorintegrated circuit 200 according to an embodiment of the invention.Configurable photo detector circuit 200 includes a photo detector array201 comprising a plurality of photo detectors, such as photodiodes,which is coupled to a switching matrix 202. A controller 204 allowsprogramming of switching matrix 202, such as using an I²C control bus,which is coupled to the switching matrix 202, to effectuate changes inthe switch configuration provided by switching matrix 202. Theprogramming can be external programming. Bus lines 206 from controller204 are generally coupled to the gates (or other control inputs) oftransistors in the switching matrix 202 to control switching. Theoutputs of switching matrix 202, generally referred to as matrixoutputs, are coupled to inputs of output block 203.

FIG. 2( a) shows an exemplary photo detector array 201 according to anembodiment of the invention having 4 banks (banks A, B, C and D), witheach bank comprising a 3×3 photo detector array. The lines between thephoto detectors represent electrical isolation between respective photodetectors, such as spaced apart on the order of several microns.Although the banks in FIG. 2( a) are shown as being the same size andshape, the sizes and shapes of the photo detectors can be differentbetween banks, and there can be similar banks at different locations onthe integrated circuit.

The array 201 is generally configured to provide a main (center) channeland two (2) side channels for PDICs adapted for optical pickup unit(OPU) applications. For example, for such a PDIC application, thecircuit would generally include a center cluster comprising one or morebanks, with the side clusters comprising one or more photo detectorbanks spaced apart on respective sides of the center cluster.

FIG. 2( b) shows a PDIC pattern layout showing photo detector centerbank 210, and a pair of side channel photo detector banks 220 and 230,that can be implemented as configurable photo detector integratedcircuit according to an embodiment of the invention to provide aconfigurable detection pattern. Center (main) photo detector bank 210 isshown comprising sectors A, B, C and D. For optimal performance, theside beam should generally land at the center of the 2 sections of theside photo detector pattern (i.e., between H&G for photo detector 220and between F&E for photo detector 230). However, for differentwavelengths, the location of the side channel photo detectors wouldgenerally need to be different for the various wavelengths for therespective side beams to land at the center of the 2 sections of theside photo detector pattern. Configurable photo detectors according toan embodiment of the invention overcome the limitation of conventionalfixed photo detector detection patterns, and in one embodiment allowingside beam centering for multiple wavelengths, such as DVD (about 650nm), CD (780 nm) and Blu-ray and HD-DVD (405 nm).

FIG. 3 shows an exemplary switching matrix 202 and output block 203shown for simplicity as being only bank A shown in FIG. 2( a), accordingto an embodiment of the invention. Switching matrix 202 comprises anarray of PMOS FETs. Connections 206 are shown from controller 204 to thegates of the PMOS FETs. Output block 203 comprises a plurality ofamplifiers, A₀₁, A₀₂ . . . A_(0X) that are dedicated to processingsignals from bank A photo detectors (A11, A12 . . . A23, A33). In oneembodiment PMOS transistors are used in switching matrix 202 becauseswitching is generally accomplished at a high bias voltage, such asaround 3 volts for a 3.3 volt power supply. Although PMOS FETs areshown, NMOS FETs can be used, or bipolar transistors of either type, orother types of switches. Electrical outputs from the respective photodetectors in bank A (A11, A12 . . . A23, A33) are shown as coupled tothe sources of PMOS transistors in the switching matrix 202 as shown inFIG. 3. Drains of the PMOS transistors in switching matrix are coupledto inputs of amplifiers A₀₁, A₀₂ . . . A_(0X) in output block 203.Outputs from respective photo detectors (e.g. A11) generally switch toone and only one output of output block 203 (e.g. A₀₁, A₀₂ . . . A_(0X)or Vref), and multiple photo detectors (e.g. A11 and A12) can beswitched to the same output (e.g. A₀₁) of output block 203. The unusedphoto detectors are preferably switched to Vref to minimize loss ofphoto current to unbiased photo detectors. “Unused”, as used herein,refers to photo detectors that are not coupled to the output block 203by switching matrix 202. Unbiased photo detectors, as used herein,refers to photo detectors that are not biased, as opposed to photodetectors in normal operation which are preferably biased at a highervoltage to increase their speed.

In certain applications, such as when a simplified PCB trace design isneeded, or based on the complexity of the photo detector patternselected by a customer, such as for a blue (405 nm) drive, there may bea requirement for switching between different photo detector banks toprovide output combinations which include photo detectors from differentphoto detector banks. As noted above, the arrangement shown in FIG. 3dedicates output block amplifiers to one of the plurality of photodetector banks. The arrangement shown in FIG. 3 thus does not allowswitching between output block amplifiers between different photodetector banks.

FIG. 4 shows a configurable photo detector circuit 500 according to anembodiment of the present invention that provides switching of outputblock amplifiers between different photo detector banks Configurablephoto detector circuit 500 adds an inter-bank switching matrix 502,which is interposed between switching matrix 202 (which is associatedwith photo detector array 201 and controller 204) and an output blockshown as 503. Inputs from switching matrix 202 to the source of PMOSswitches comprising inter-bank switching matrix 502 are shown insimplified form as A1, B1 and C1. A1 can represent combined outputs fromphoto detectors A11, A12 and A13 shown in FIG. 2, for example.Inter-bank switching matrix 502 is controlled by controller 204, such asusing a serial control interface, or a separate/dedicated serial controlinterface. The outputs from inter-bank switching matrix 502 are coupledto output block 503. Inter-bank switching matrix allows outputs fromphoto detectors in any bank (e.g. A, B, C, or D) to be coupled to any ofthe output amplifiers, and in one embodiment, in any combination.

Configurable photo detector circuits according to an embodiment of thepresent invention can be both I²C master and slave. For example, theconfigurable photo detector circuit can either be programmed throughI²C, or read configuration data from EEPROM through I²C. The serialinterface used however is not limited to I²C, since it can be anyinterface that allows external user programming of the device.

The amplifier gain, bandwidth and offset for amplifiers in output blocks203 and 503 can also be externally adjusted. In addition, the amplifiergain, bandwidth and offset for amplifiers in the output block, such asA01 and A02 shown in FIG. 3, can be externally adjusted. FIG. 5 shows asimplified exemplary circuit arrangement 610 which permits externaladjustment of dc and ac parameters of amplifier 630, according to anembodiment of the invention. Offset adjustment is accomplished usingvariable current source 605, while gain and bandwidth of the outputamplifiers can be modified, for example, using the variable feedback RCnetwork shown comprising a variable capacitor 615 and variable resistor620. As known in the art, externally applied digital inputs to pinoutpins provided can be used to set the current source level, as well asthe feedback resistor and capacitor values, and the gain. For example,in one embodiment, the gain can be set by a digital input based on atriple level input control.

FIG. 6 shows portions of an information recording/reproducing apparatus800, including a main circuit board 802, a flex cable 804 and an opticalpick-up unit (OPU) 806 according to an embodiment of the invention. Asdescribed below, the OPU 806, and thus apparatus 800, can be prototypedusing one or more configurable photo detector circuits according to thepresent invention to enable rapid design of PDICs and/or PMICs used inOPU 806, such as PDICs and/or PMIC ASICs. The description below ofapparatus 800 is based on commonly assigned U.S. Publication No.20040202072 to Rees et al. The main board 802 includes a controller 808and an analog front end (AFE) 810. The OPU 806 includes a laser driverintegrated chip (LDIC) 812, a power monitor integrated chip (PMIC) 814and a photo-detector integrated chip (PDIC) 816. As noted above, PMIC814 and/or PDIC 816 can be ASICs that have detection patterns that aredetermined using configurable photo detector circuits according to anembodiment of the invention.

The LDIC 812 controls the current to laser diodes 830 and 832, causingone of the laser diodes 830 or 832 to output a light signal that, afterbeing appropriately focused by an optical system (not shown), isincident on an a optical media disk (not shown). In the embodimentshown, the LDIC 812 includes an automatic power control (APC) portion820, a running optical power control (ROPC) portion 822 and a writestrategy generator 824.

The LDIC 812 is shown as being capable of driving two different laserdiodes 830 and 832. The LDIC 812 can also drive more than two laserdiodes. For example, the LDIC 812 can be capable of driving a firstlaser diode that outputs a wavelength of 780 nm, a second laser diodethat outputs a wavelength of 655 nm, and a third laser diode thatoutputs a wavelength of 405 nm. Of course, the laser diodes can outputlight signals of other wavelengths.

The write strategy generator 824 implements an appropriate writestrategy, which may depend, for example, on the media, DVD or CDstandards, and/or speed being supported. The ROPC 822 uses (e.g.,modulates) the APC signals to compensate for variations in the opticalmedia. The APC 820 controls the laser diode to compensate for changes inthe laser diode's characteristics.

A photo-detector 834 detects optical signals output by laser diode 830or 832 before the light signals reach the media, and provides a signalrepresentative of the detected intensity to the PMIC 814. In contrast,multiple photo-detectors 836 generally detect the optical signal thathas been reflected from the media (e.g., DVD, CD or Blu-ray media). Aninformation signal produced by photo-detectors 836 includes user data(e.g., to be provided to a host in response to a read request from thehost), servo information (e.g., used for servo control) and amplitudeinformation. Samples of the amplitude of the information signal producedby the PDIC 816 are provided to the ROPC 822, which adjusts the powersignal and current signal in the APC to compensate for variations in themedia, as discussed below. Samples of the signal produced by thephoto-detector 834, in contrast, are used by the APC 820, such as tocompensate for environmental variations and aging of the laser diodes830 and 832.

As shown in FIG. 6, the PMIC 814 and the PDIC 816, each include theirown dedicated offset, gain and sample-and-hold (gain/SH) circuits 826and 828. This enables the PMIC 814 to amplify and sample the analogmonitoring signal produced by photo-detector 834. This also enables thePDIC 816 to amplify and sample the analog information signal produced byphoto-detectors 836.

The samples of the information signal produced by the PDIC 816 are sentup the flex cable 804 to the AFE 810, which performs front end signalprocessing, such as converting analog data to digital data, andcontrolling focusing and tracking servo loops. The AFE 810 provides adigital signal to the controller 808, as shown in FIG. 6.

In summary, configurable photo detector circuits having externallyconfigurable photo detector detection patterns according to theinvention have a number of significant advantages, many beingadvantageous for prototyping an OPU including, but not limited to:

i) ability to integrate multiple PDICs previously required to processmultiple wavelengths (e.g. different media types) into a single IC;

ii) ability to optimize the photo detector detection pattern for eachmedia type;

iii) improved signal to noise ratio (SNR) with optimized photo detectorsize/patterns;

iv) greater optics design flexibility, and

v) improved PMIC sensitivity since larger beam spot may be used to relaxoptical alignment and accompanying lower power density. Users canconfigure the PMIC to combine multiple (e.g. all) photo detectorsegments to form a larger area detector to increase device sensitivity.

Embodiments of the invention can be applied PDICs, PMICs, or IPUsincluding PDICs, and/or PMICs, for conventional CD/DVD as well as towrite/read emerging Blu-Ray discs and/or HD-DVD format discs, withsingle or multiple layer formats. Embodiments of the invention may alsobe applied to generic optical storage technologies or other applicationsthat incorporate similar photo-sensing techniques.

As noted in the Background above, one significant problem duringdevelopment of PDICs and PMICs for OPUs relates to the need to select aphoto detector detection pattern before testing the overall system,since available photo detectors provide a fixed detection pattern andmodeling is not currently possible. Historically, this type ofdevelopment was accomplished by simultaneously developing the opticsdesign and light path, and developing a customized photo detectorpattern to match the optics configuration. This development cycle mayconsist of multiple iterations and through a combination of historicaldesign considerations, near-modeling of the optics and electricalsystems, and successive trial and error iterations, an optimal orpseudo-optimal configuration and optics design is eventually generallyreached. The primary disadvantage of this method is the long cycle timeswhen the iterative process requires several new photo detector patternor optics system, as it typically does in certain applications. Asdescribed above, configurable integrated circuits according to thepresent invention provide an externally programmable photo detectorpattern for PDICs and PMICs.

Configurable integrated circuits according to an embodiment of theinvention embodied as configurable PMICs will now be described in anexemplary use for rapidly prototyping of an OPU to provide acceleratedcustomer development which enables reduction in risk, acceleratedtime-to-market, and to produce cost effective solutions that can spanmultiple product generations. Commercially available complete referencedesign platforms including firmware and board support packages can beobtained. The development platform is operable to adjust or configurevarious parameters of the PDIC, including output voltage offsets, gainsfor the various read/write modes and media types, as well as the photodetector pattern or configuration. This programmability provides thecustomer with an increased level of flexibility and performance whendesigning the hardware of the optical system. In the specific example ofthe configurable photo detector pattern, the design of the optics pathand the photo detector pattern shape and locations are closely related.

FIG. 7 is a flow chart showing an exemplary method of prototyping an OPUusing configurable photo detector circuits 700 according to anembodiment of the invention. At block 705, a standard or base photodetector pattern is selected. An example would be a simple quad arrayphoto detector for the main channel and a dual or quad configuration forthe two side channels generally used. At block 710, at least oneperformance-related parameter for the OPU is evaluated while theconfigurable photo detector circuit is configured in the standard orbase detection pattern. The process of finding an acceptable photodetector configuration can comprise evaluating the output of the photodetector channels, evaluating SNR, optical waveforms, system parameterssuch as BER (bit error rates), servo tracking accuracy, each separatelyfor one or more modes, such as CD, DVD and Blu-ray and HD-DVD modes. Atblock 715, a new detection pattern different from the standard or basedetection pattern is selected. For example, as described above, a serialinterface (I²C, SPI, or other) can be used to program the configurationof the detector pattern. The performance-related parameter is thenre-evaluated at block 720 while the configurable photo detector circuitis configured in the new detection pattern. At block 725 it isdetermined whether the performance criteria is satisfied. If thecriteria is determined to not be satisfied, the method returns to block715 where another new detection pattern different is selected, and theperformance-related parameter is re-evaluated at block 720, etc. If thecriteria is determined to be satisfied, the method reaches block 730,wherein the criteria satisfying detection pattern is established for usein a fixed detection pattern photo detector comprising integratedcircuit.

Depending on the results of the measured parameters and system levelperformance, the customer is able to modify the configuration and shapeof the detection pattern of the building blocks in the configurablephoto detector circuit in near real-time, thereby being able to arriveat a more optimal photo detector configuration much faster, with lowerdevelopment cost, and generally being able to achieve a more opticalconfiguration or solution given the ability to modify the PDIC detectionpattern quickly and easily. This aspect provides the designer with agreater degree of freedom, allowing them to focus on the hardwareportion of the optics design by gaining flexibility on the electricaland key PDIC component of the system.

As noted in the background, a significant issue the optical storageindustry recently experienced is related to the introduction ofinterference patterns on the servo tracking signal caused by unwantedoptical reflections when reading dual layer Blu-ray media. Thedevelopment cycle to resolve this issue is known to be long, largely inpart due to the inability to test different PDIC photo detector patternsand to rapidly evaluate the output or results. Using configurable photodetector circuits according to an embodiment of the present inventionwhich provide a highly flexible photo detector grid array, customers canevaluate different configurations of the photo detector side channels toprovide different detection patterns, to see the immediate impact toservo tracking signal integrity by allowing instant repositioning andconfiguration of the photo detector patterns. While the method accordingto this embodiment of the invention may be iterative, given the nearreal-time nature of the feedback and subsequent photo detector detectionpattern changes, this process generally takes days instead of months oreven years. Once a performance criteria satisfying detection pattern isidentified, a mask set may be generated to implement the criteriasatisfying detection pattern, and the mask set then used for productionof a fixed detection pattern photo detector circuit.

Moreover, the future of optical storage and optical systems in generalis generally rapidly changing. As the industry moves toward even greaternumber of data layers (beyond dual layer Blu-ray and HD-DVD media) anddifferent technologies, the same problems with greater intensity, or newproblems affecting the photo detector performance and requirements willlikely emerge. Having the ability to breadboard a photo detector deviceusing configurable photo detector circuits according to the invention isexpected to prove invaluable in such situations.

Although photo detectors herein have been described using photodiodesoperating in photovoltaic mode, the invention may also be practiced withphotodiodes which operate in photoconductive mode since eitherphotovoltaic or photoconductive mode outputs are adapted to be coupledto conventional amplifier arrangements. However, more generally, thosehaving ordinary skill in the art will realize that photo detectorsaccording to the present invention can comprise other photo detectortypes.

In the preceding description, certain details are set forth inconjunction with the described embodiment of the present invention toprovide a sufficient understanding of the invention. One skilled in theart will appreciate, however, that the invention may be practicedwithout these particular details. Furthermore, one skilled in the artwill appreciate that the example embodiments described above do notlimit the scope of the present invention and will also understand thatvarious modifications, equivalents, and combinations of the disclosedembodiments and components of such embodiments are within the scope ofthe present invention.

Moreover, embodiments including fewer than all the components of any ofthe respective described embodiments may also within the scope of thepresent invention although not expressly described in detail. Finally,the operation of well known components and/or processes has not beenshown or described in detail below to avoid unnecessarily obscuring thepresent invention.

One skilled in the art will understood that even though variousembodiments and advantages of the present Invention have been set forthin the foregoing description, the above disclosure is illustrative only,and changes may be made in detail, and yet remain within the broadprinciples of the invention. For example, some of the componentsdescribed above may be implemented using either digital or analogcircuitry, or a combination of both, and also, where appropriate may berealized through software executing on suitable processing circuitry.The present invention is to be limited only by the appended claims.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the following claims.

We claim:
 1. A method of using a configurable photo detector circuit,comprising: receiving a first input to select a first switchconfiguration from a plurality of different switch configurationsprovided by a switching matrix; configuring the switches of theswitching matrix to implement the selected first switch configurationfrom the plurality of different switch configurations provided by theswitching matrix; receiving light at a plurality of photo detectors;converting light into a first set of electrical signals at the pluralityof photo detectors; and selectively directing the first set ofelectrical signals to any of a first plurality of amplifiers based onthe selected switch configuration.
 2. The method of claim 1, whereinreceiving the input comprises transferring data to a data transfercontroller using an I²C interface.
 3. The method of claim 1, furthercomprising: directing a first photo detector output to a first amplifierinput; and directing a second photo detector output to the firstamplifier input.
 4. The method of claim 1, further comprising: adjustingat least one of the gain, bandwidth, and offset of the plurality ofamplifiers.
 5. The method of claim 1, wherein the first switchconfiguration is configured for a first wavelength of light.
 6. Themethod of claim 1, further comprising: receiving an input to select asecond switch configuration from the plurality of different switchconfigurations provided by the switching matrix; configuring theswitches of the switching matrix to implement the selected second switchconfiguration of the plurality of different switch configurations by theswitching matrix; receiving light at a second plurality of photodetectors; converting light into electrical signals at the secondplurality of photo detectors; and selectively redirecting the electricalsignals to various amplifiers from the plurality of amplifiers based onthe second selected switch configuration.
 7. The method of claim 6,wherein the first switch configuration is configured for a firstwavelength of light; and wherein the second switch configuration isconfigured for a second wavelength of light.